Since the sdam changes are rather extensive, it would be helpful to have the logging improvements backported to 2.6 for both users that may not wish to upgrade to 2.7 right away as well as for users who experience issues with 2.7 and wish to compare 2.7 behavior against 2.6 behavior.

Specifically the following two changes are desired:

1. The warning when removing servers from topology.
2. The warning when the last server is removed and topology is left with no servers.